Applicant claims priority under 35 U.S.C. xc2xa7119 of AUSTRIAN Application No. A 2050/99, filed on Dec. 6, 1999. Applicant also claims priority under 35 U.S.C. xc2xa7120 of PCT/AT00/00327, filed on Dec. 5, 2000. The international application under PCT article 21(2) was not published in English.
1. Technical Field
The present invention relates to a machine for sowing individual seed grains having at least one hopper open towards a vertical sowing disc, whereby the sowing disc comprises a stationary disc body exposed to suction on the side averted from the hopper, having at least one guiding slot and also comprising a driveable conveyor disc resting on the side of the hopper on the disc body with carrier slots distributed over the circumference and also extending over the radial extension area of the guiding slot, which together with the guiding slot form the aspiration apertures in the overlapping area for the seed grains which can be discharged from the seed hopper along the guiding slot.
2. Prior Art
In order to ensure proper thinning of seed grains and even delivery of the thinned seed grains, machines for sowing individual seed grains (DE 31 03 101 C2, US 4 896 616 A) are known to divide the sowing discs into a stationary disc body and a conveyor disc resting on this disc body which is provided with radial carrier slots. Because the disc body is provided with a guiding slot extending over a circumferential area forming a discharge path for the die seed grains, which is suctioned on the side averted from the conveyor disc, aspiration apertures for the seed grains, which are distributed along the guiding slot from the hopper attached to the sowing disc, are located in the overlapping area of the carrier slots with the guiding slot. The seed grains suctioned onto the aspiration apertures come into contact with both the stationary disc body and with the rotating conveyor disc, which leads to rotation of the suctioned seed grains, to the effect that one of the seed grains suctioned to a aspiration aperture covers the aspiration aperture while the remaining seed grains are held back, and while the remaining seed grains fall back into the hopper. Since the suctioned seed grains tend to be drawn deeper into the aspiration apertures on account of their rotation, somewhat uneven separation of the seed grains thinned out by the sowing disc at the end of the guiding slot has to be reckoned with. For this uneven seed discharge not to result in uneven planting distances by the machine for sowing individual seed grains, a bucket feeder rotating with the conveyor disc is provided, in turn providing automatic discharge at preset intervals independent of the seed separation. In addition, the discharge rate and thus the sowing rate of such a machine for sowing individual seed grains is restricted on account of the thinning procedure requiring the grain to rotate.
The object of the invention is accordingly to provide a machine for sowing individual seed grains of the type described at the outset in such a way that the discharge rate of the thinned out seed grains can be considerably increased, without having to dispense with secure thinning, and also with seed grains having comparatively large differences in dimensions.
The present invention solves this task by the fact that the angle between the longitudinal edges of the carrier slots and the guiding slot in the overlapping area of these slots at least on one slot side along the guiding slot are repeatedly changed within a predetermined angle range.
Because the angle between the longitudinal edges of the carrier slots bordering the aspiration apertures and of the guiding slot changes repeatedly whenever the conveyor disc is rotated, the aspirated seed grains are also turned around in the vicinity of the aspiration apertures over the longitudinal edges of the criss-crossing slots, which extensively supports the thinning out effect. The improved thinning of the seed grains contributes the desired increase in output, because the seed grains are properly thinned out also when the conveyor disc is rotated at higher speeds, and independently of relevant differences in size of the seed grains. As the aspirated seed grains are being rotated and pulled through the longitudinal edge profile of the slots in the vicinity of the aspiration apertures, this occurs independently of seed size.
The longitudinal edge profile of the slots in the conveyor disc and/or in the disc body can vary and be adapted to the geometric ratios determined by the seed to be sown. It is required that not all seed grains are displaced from the aspiration area, so that the angle between the longitudinal edges of the crisscrossing slots bordering the aspiration apertures should be altered in a permissible angle range. If the slot edges have a corrugated profile, these requisites can be easily met. The range and lengths of these waves of the slot edges are selected advantageously depending on the seed material to be sown. The slot edges can also be provided to form the corrugated profile with edge-side depressions, by means of which an additional movement vertical to the sowing disc can be exerted on the seed grains, effectively supporting the thinning out procedure.
Particularly advantageous discharge ratios result for the seed, if the guiding slots in the disc body are not as wide as the carrier slots in the conveyor disc. When the width of the carrier slots is adequate this measure enables the seed grains to lie flat on the disc body between the longitudinal edges of the carrier slots, which is why the tendency of the seed grains to penetrate more deeply into the guiding slot can be extensively prevented. In this case the guiding slot can be configured correspondingly narrow. With the seed grains lying flat on the sowing disc separating the seed grains is facilitated by the sowing disc, if the seed grains exit from the suctioned area of the guiding slot and then fall from the sowing disc, so that an adequately limited separation point of the seed grains by the sowing disc can be reckoned on. This fulfils all requirements for being able to dispense with a bucket feeder for evening out the seed discharge. This applies in particular if the guiding slot remains unaffected by suction in the vicinity of a downwards directed discharge end, since said unsuctioned discharge end of the guiding slot forms additional guide help for the seed grains separating from the sowing disc.
To be able to safely interrupt the seed discharge in spite of rotation of the conveyor disc dependent on the travel speed of the machine for sowing individual seed grains, at least one nozzle directed towards the guiding slot can be provided in the vicinity of a section of the guiding slot rising from the floor area of the hopper, which, when impacted, uses compressed air to blow the seed grains still entrained after aspiration impact of the guiding slot is switched off with the conveyor disc by the sowing disc back into the hopper. While impacting of the guiding slot is interrupted in the section under the nozzle, aspiration of the guiding slot is maintained in the section attached to the nozzle at least until the last seed grain, not yet blown away by the sowing disc, is discharged.